Comparison study of fly ash reinforced AA6061 composites using press sinter extrusion and press extrusion approaches

Abstract

This paper presents the preliminary results obtained in developing a powder metallurgy process involving an approach based on the use of press (compaction) and sintering together with subsequent extrusion on one hand and press and extrusion on the other hand. Two systems have been compared: an unreinforced AA6061 alloy (matrix) and AA6061-2 wt.% fly ash particulate composite. Mechanical mixing of the matrix powder, obtained from elemental powders, and particulate reinforcement was followed by compaction. Pressurisation was carried out at 345 MPa with zinc stearate as die wall lubricant. Some green compacts were extruded subsequently at 5–10 mm min⁻¹ rate with a reduction ratio of 16:1 at 500°C. And some were sintered at 620°C for 4 h before extrusion. From XRD, SEM EDAX and mechanical testing studies it was observed that the press extruded samples were showing improvement in density, hardness, 0·2% proof stress and tensile strength over press sinter extruded samples.